Interactive Motion Technologies, Inc. is the exclusive licensee of robotic technology developed at the Massachusetts Institute of Technology. We have successfully redesigned an alpha-prototype developed at MIT for planar movement, which we are currently commercializing under the trade name of InMotion2. The goal of this proposal is to develop a commercially viable, three-degree-of-freedom robot for neuro-rehabilitation of the wrist. To ensure gentle, compliant and stable behavior the robot will feature a low intrinsic mechanical impedance (i.e., be highly back-drivable). To provide adjustable and/or varying degrees of assistance to the patient, the robot controller will provide a (programmable) rotational impedance (i.e., its "firmness" will be adjustable.) The technical objectives of this SBIR project are to: (1) Re-design the alpha-prototype wrist robot for commercial production, so that the $40,000 component cost is reduced to approximately $15,000. To preserve and even enhance functionality, "focus-group" evaluation sessions will be conducted that, with guidance from expert therapists, will elicit information and observations on the alpha prototype?s strengths and weaknesses. (2) Design and implement a spatial impedance control algorithm to operate the wrist robot. Impedance control refers to using a control system to impose a desired behavior at a specified port of interaction with a robot, in this case the attachment of the robot to the patient?s wrist, Impedance control was conceived in the early 1980?s by one of our advisors (Prof. Hogan); it has recently been extended to include spatial impedance control, which was developed and tested by one of Prof. Hogan?s former students.